Synergistic Al3+ Doping and Multilayer ZnS Shell for Enhanced Photoluminescence and Long-Term Stability of Water-Soluble ZnSe Quantum Dots

Water-soluble ZnSe quantum dots (QDs) typically suffer from limited photoluminescence (PL) efficiency and poor long-term stability due to intrinsic defects and surface traps. Here, we report a strategy combining Al3+ doping with stepwise multilayer ZnS shell growth. The stepwise precursor injection ensures uniform shell formation, while Al3+ incorporation suppresses defect-related recombination within the ZnSe core. The resulting ZnSe:Al/ZnS/ZnS/ZnS QDs exhibit a PL quantum yield of 23.24% and an average lifetime of 129.28 ns. They retain 91% of their initial PL intensity after 200 days under ambient conditions. Mechanistic analysis indicates that defect regulation and multilayer shell passivation synergistically promote band-edge radiative recombination over defect-assisted pathways. This work provides a strategy for simultaneously regulating defect states and surface stability in water-soluble semiconductor QDs.